1. Field of the Invention
The present invention generally relates to a management system for a water-barrier sheet of double layer construction to be arranged in the bottom of a waste treatment plant, an impounding reservoir, and so forth, as which is divided into a plurality of hermetically sealed divisions. More specifically, the invention relates to a management system for a water-barrier sheet capable of identification of a damaged portion and preventing underground penetration of sewage through the damaged portion.
2. Description of the Related Art
In a land-filling type waste treatment plant, for example, where industrial and/or nonindustrial waste are disposed, it has been an obligation by applicable regulations to construct a water-barrier in the bottom of the field for preventing pollution due to underground penetration of sewage leaking from the waste. As such water-barrier, it has been typical to arrange a flexible synesthetic resin type or rubber type water-barrier sheet in view of economy and water-barrier characteristics. Also, in the bottom of facilities accumulating a large amount of water in a recessed portion, such as a water hazard in a golf course, an impounding reservoir, a holding pond, a pool and so forth, a water-barrier sheet similar to that employed in the waste treatment plant has been arranged for preventing leakage of the accumulated water.
However, in recent years, environmental pollution has been caused by leakage of the sewage and/or accumulated water due to rupture of the water-barrier sheet. As a solution for this, installation of a double layer type water barrier has been considered for enhancing safety by preventing leakage of sewage by a second layer sheet even when a first layer sheet is damaged.
As improvement of this idea, Japanese Laid-open Patent Publications (Kokai) Nos. 6-63525 and 6-63526 disclose an advanced type double layer water-barrier sheet which can provide higher reliability. In such arrangement, the double layer type water-barrier sheet is divided into a plurality of divisions isolated from each other in water-tight fashion so that even when the water-barrier sheet in one division is damaged, water-barrier performance in other divisions can be maintained with certainty. In addition, a water detecting means is provided in each individual division so that a damaged portion can be identified when leakage occurs so as to repair the damage by introducing a solidifying agent into the division identified as damaged.
Such arrangement is advantageous from the viewpoint of construction cost and operating cost. Namely, in the proposed construction, only a double layer water-barrier sheet is required initially. Therefore, the construction cost can be maintained at a level comparable with the conventional water-barrier construction. On the other hand, once a damaged division in the water-barrier sheet is identified, all that is required is to inject water stop agent into the damaged division. Therefore, the area to which the water stop agent is applied is limited so that the amount of the water stop agent to be used is significantly reduced. This is particularly advantageous when the facility where the water-barrier sheet is provided is large and thus the water-barrier sheet is required to cover a huge area.
However, in the related art, there is no well-systemized and well-established management system for managing damage and maintenance of the water-barrier sheet. In general, a waste treatment plant, an impounding reservoir and so forth are constructed over quite large areas. Therefore, the area to be covered with the water-barrier sheet also is quite large. Management of such water-barrier sheet by manual operation may become labor intensive and cause a significant increase of operating costs. There is a strong demand for a systematized management system for managing such double layer water-barrier sheet.